Aim and Objective: The aims were to evaluate the root canal debris removal after irrigation with EndoVac system and to compare its efficacy with Max-i-Probe needles.Materials and Methods: Fifteen matched pairs of single canalled vital teeth with mature apices indicated for extraction were selected. After working length determination and biomechanical preparation, the teeth in the right quadrant were irrigated with EndoVac system and with Max-i-Probe needles in the left quadrant using 3% NaOCl and 17% ethylenediaminetetraacetic acid. Teeth were extracted and marked at 1 and 3 mm from working length and decalcified in Kristenson's solution. Stained histologic slides were observed under trinocular research microscope. Wilcoxon signed-rank test was used for statistical analysis. The statistical significance was set at P < 0.05 and the analysis was performed using SPSS version 11.0 software.Results: No statistical significant difference was found at 3 mm level between the groups. Group I had significantly less debris at 1 mm level.Conclusion: EndoVac performed better in removing debris from the apical thirds of root canals.

The challenge in achieving successful endodontic treatment lies in a variety of factors such as cleaning, shaping, and three-dimensional obturation. Root canal treatment usually fails when treatment falls short of acceptable standards. Persistence of microbes, organic, and inorganic debris in the root canal system is one of the major factor associated with endodontic failure. [1]

Debridement of the root canal system is essential for endodontic success. Because of the complexity of root canal anatomy and the limitations of instrumentation, irrigation has gained increasing attention. Removal of the dentinal debris from apical areas of the root canals depends upon the efficacy of an irrigation system. [2]

Traditionally, the most common way in which the irrigant has been introduced into the root canal was through a needle connected to a syringe. [3] Among the various needle tip designs, the Max-i-Probes have shown better results and long-term clinical success. [4],[5] These irrigation probes have side port dispersal and a rounded tip. The side port dispersal design produces upward flushing motion for complete canal irrigation. Closed and rounded end reduces the risk of apical extrusion. [3],[6] For this reason, the Max-i-Probes were selected in our study.

Adjuncts to irrigation such as sonic, ultrasonic and subsonic activation have been introduced in an effort to improve the delivery and efficacy of irrigants to the apical third in order to improve the cannal cleanliness. [7] The EndoVac is one among the recently introduced irrigation device that works on negative pressure, which draws irrigation solution apically through suction from the high-volume evacuation of the dental unit. [8],[9] The recommended protocol for the use of apical negative pressure irrigation includes two main phases: Macro and micro irrigation. This system is composed of a macro- and micro-cannula that make the irrigating solution circulate due to the difference of pressure caused by the vacuum inside the root canal system. [10] The negative pressure overcomes the shortcomings encountered with positive pressure: Lack of clean canal in the last few millimeters of the root canal system and the omnipresent danger of irrigant extrusion. Hence, the purpose of this study was to evaluate the debris removal efficacy of EndoVac and to compare it with the routinely used syringe irrigation.

Materials and methods

Patients visiting the outpatient department fulfilling the following conditions participated in this study.

Patients with noncontributory medical history.

Patients with matched pairs of single canal, noncarious vital teeth with mature apices indicated for extraction due to orthodontic, periodontic or prosthodontic considerations.

Clinical examination was performed and vitality of the teeth was confirmed using electric pulp tester. The treatment and study design was explained to the patients. All patients who agreed to participate in the study signed an informed consent for which approval was obtained from Ethical Committee of Chhattisgarh Ayush and Health Science University, Chhattisgarh, India.

After adequate anesthesia, the endodontic procedure was carried out under strict aseptic conditions and rubber dam isolation. Access to the pulp chamber and canal was made. A #10 K file was placed in the canal and working length was established using radiovisiography. The canals were prepared with K3 rotary files in a crown down pressureless technique.

Fifteen matched pairs of teeth were divided into two groups. In the right tooth of each pair (Group I), irrigation solution was discharged by EndoVac and the left tooth (Group II) was irrigated using Max-i-Probe irrigating needles. Each tooth received an equal volume and amount of time for irrigation.

For EndoVac group, irrigation began during the use of Gates Glidden drills. One milliliter of 3% NaOCl was used to replenish the irrigant in the pulp chamber after each rotary NiTi instrument. After reaching working length with the master apical file, the canal was macro and micro irrigated.

The macroirrigation of each canal with NaOCl was accomplished over a 30-s period. This was done by using the EndoVac delivery tip. The canal space was then left undisturbed, full of irrigant for 60 s. Three cycles of microirrigation was followed. During a cycle of microirrigation, the pulp chamber was maintained full of irrigant, while microcannula was placed at working length for 6 s. The microcannula was then positioned 2 mm from working length for 6 s and moved back to working length for 6 s. This up-down motion continued until 30 s had elapsed, thus ensuring 18 s of active irrigation directly at working length.

After 30 s of irrigation, the microcannula was withdrawn from the canal to ensure that the canal remained totally filled with irrigant and was left undisturbed for 60 s. This completed one microirrigation cycle. The first microcycle used 3% NaOCl, the second 17% ethylenediaminetetraacetic acid (EDTA) and the third 3% NaOCl. The microcannula was left without replenishment to remove excess fluid. Paper points were used to dry the canal.

In Group II irrigation was performed by 30-gauge Max-i-Probe irrigating needle. A 1 ml flush of 3% NaOCl was used. This was done with the needle placed no closer than 2 mm from working length. A small constant apical-coronal movement of the needle was maintained during expression of irrigant. After instrumentation to the master apical file size, irrigation with NaOCl for 30 s was accomplished and irrigant was left undisturbed for 60 s.

Further the needle was moved up and down in constant motion for 30 s. 3% NaOCl was used and left untouched for 60 s, followed by 17% EDTA and last irrigant with 3% NaOCl using the same method for the same amount of time. Paper points were used to dry the canal.

A piece of gauze was placed into the pulp chamber of each tooth and the tooth was extracted. The gauze was removed, and a canal was gently irrigated with phosphate buffered saline followed by formalin. The teeth were marked at 1 and 3 mm from working length and were decalcified in Kristenson's solution (102 g sodium formate, 1500 ml hot tap water, 515 m formic acid, and 925 ml cold water) for 1 week. The decalcified roots were cut with a scalpel at the 1 and 3 mm marking from working length.

Six micron histologic sections were made from each root and stained. Each slide contained serial sections of either 1 or 3 mm level of one of the experimental teeth. Before viewing the sections, any identification on the slide was masked. The sections on each glass slide were compared by using a trinocular research microscope at ×4 magnification. The section containing the greatest amount of canal debris was digitally photographed [Figure 1] and [Figure 2]. All images were analyzed by Image Analysis Software (Lynx Biolux [Lawrence and Mayo, India Pvt. Ltd.]). The amount of debris left in the canals was quantified as a percentage of the canal lumen area. The data were statistically analyzed to compare the percentage of remaining debris between the two irrigation techniques at each of the two levels using Wilcoxon signed-rank test. The statistical significance was set at P < 0.05 and the analysis was performed using SPSS version 11.0 software [SPSS Inc., Chicago]. The methodology adopted by us was based on studies conducted by Nielsen and Baumgartner [11] and Siu and Baumgartner. [12]

Figure 1: Histologic picture of the slide at 1 mm from the working length in the EndoVac group

The mean area of the canals in both groups was calculated and compared among each pair using paired t-test [Figure 3]. The amount of debris remaining at the two levels in both groups was calculated, and it was quantified as a percentage from the mean area of the canal [Figure 4]. The percent of debris remaining at 1 and 3 mm from the working length in Groups I and II was compared for statistical significance using Wilcoxon signed-rank test. The statistical significance was set at P < 0.05 and the analysis was performed using SPSS version 11.0 software.

Figure 3: Bar chart showing the mean canal area at 1 and3 mm from working length in two groups

In this study, matched pairs of teeth were taken so as to control the variable of canal dimensions between the two groups for better statistical comparison [11] and vital teeth were chosen to help reduce the variability of debris. [12] Curvature of roots and presence of more than one canal may affect the efficacy of irrigation. [13] Therefore, only single rooted teeth with straight canals and mature apices were selected for the study.

Canal lumen area was calculated first and later the amount of debris left in the canal was quantified as the percentage of canal lumen area. The values obtained for the canal lumen areas for both the groups at 1 and 3 mm from the working length served the purpose of selecting matched pairs of teeth [Table 1]. This helped to control the variable of canal dimensions between the groups for better comparison.

Table 1: Area of canal at 1 and 3 mm distance from working length in two study groups

The method of determining the percentage of debris used in this study removes the subjectivity of some previous studies where evaluators gave canals a score of light, moderate or heavy for the amount of remaining debris. The method used here gives the amount of remaining debris as a percentage of the total area of the canal. [14],[15]

In Group I, the mean percentage of debris was found to be 30.25 (27.17 ± 9.78) at 1 mm from the working length [Table 2]. Better results in this group may be attributed to the apical suction effect of pulling endodontic irrigants down and along the walls of the root canal system. This creates a rapid turbulent cascading effect, as the irrigants are forced to flow between the canal walls and the external surface of the microcannula. This turbulent action creates a current force, while the position of the microholes directs this fast flowing stream of irrigant as close as 0.2 mm from working length before reversing the irrigants direction up the microcannula. Throughout this procedure, the vacuum pressure pulls micro particles out of the root canal system. [16]

In Group II, the mean percentage was found to be 44.52 (42.49 ± 13.68). The probable reason for higher scores may be due to the placement of needle no closer than 2 mm from the working length in order to avoid hypochlorite accidents. [14],[17] The difference in the mean percentage of debris between Groups I and II was statistically significant (P < 0.05). Our results corroborate with similar studies conducted by Siu and Baumgartner and Shin etal. [12],[16]

Table 2: Percent of debris remaining at 1 and 3 mm distance from working length in two study groups

At 3 mm from the working length in Group I, the mean percentage of debris was 20.38 (21.61 ± 6.27). Better efficiency of the EndoVac at this level could be due to the macrocannula design. The push pull motion of a plastic macrocannula in the canal generates higher intracanal pressure changes during pushing movements leading to more effective delivery of irrigant to the untouched surfaces. [18]

In Group II, the mean percentage was 21.08 (19.63 ± 4.95). Although the Max-i-Probe needles penetrated and delivered irrigant, the needles do not provide a negative pressure to pull the residual debris out of the canal. The disruption or detachment of debris cannot ensure their removal unless there is a favorable irrigant flow to carry them towards the canal orifice. This might explain the reason for higher scores in Group II.

Although there was no statistical significant difference (P > 0.05) observed regarding the remaining debris in both the groups, EndoVac proved to be more effective when compared with the Max-i-Probes in removing debris from apical portions of the canal. Heilborn et al. in their study compared the EndoVac system to the Max-i-Probe for root cannal cleaning efficacy and found that EndoVac system perform better than Max-i-Probe. However, no significant difference was found between groups at 3 mm level. [19]

Saini et al. have also concluded that EndoVac irrigation system showed significantly less debris than NaviTip and Max-i-Probe at both 1.5 and 3.5 mm levels. [20] However, in this study, both the delivery systems were not able to remove the debris completely from the root canals.

The only disadvantage in using the EndoVac is the blockage of the microcannula. [21] During this study, the holes of the microcannula were constantly checked as clogging of the holes may affect the efficacy of irrigation. The blocked holes were made patent with a positive pressure rinse, or the cannula was replaced.

Further research is warranted because no currently available irrigation systems consistently remove all the debris from the root canals. Curved and narrow root canals pose difficulty in cleaning the canal when compared to straight single roots. Further, the conclusions are based on a sample of 15 teeth in each group. Post-hoc power analysis was performed for the results obtained at 1 mm level. The estimated effect size based on the mean percent reduction at this level was 1.23. Assuming that the effect holds even for population, the estimated power with the present sample size and 5% significance level was 0.88, which was sufficient to justify the significance. However, to ascertain the significance of difference in percent reduction between two methods at 3 mm level, for the effect size of ~0.4, the present sample size could provide power of 0.18, which was too low. More samples should be undertaken to evaluate the efficacy of these irrigation systems in difficult canals.

Saini M, Kumari M, Taneja S. Comparative evaluation of the efficacy of three different irrigation devices in removal of debris from root canal at two different levels: An in vitro study. J Conserv Dent 2013;16:509-13. [PUBMED]